1. Field of the Invention
The present invention relates generally to the field of guard members for shielding saw operators from blades. More specifically, it relates to a pivoting guard for use on a circular saw blade mounted on an extendable arm and motor assembly overhanging a saw table. The guard apparatus takes the form of a channel member rotatably mounted on the motor assembly and over the blade, preferably within a conventional, stationary guard member, which can be rotated to expose the blade as the blade approaches a work piece and rotated to cover the blade when a cut in the work piece is completed. The guard apparatus preferably includes an air driven piston and cylinder having a piston shaft connected to the pivoting guard, to automatically withdraw the piston shaft and thereby rotate the guard to an open position, and a radially protruding cam portion on the guard against which a lever rides to operate a switch to detect when the guard is fully open, and then to automatically extend the piston shaft to close the guard.
2. Description of the Prior Art
There have long been guard members for shielding people from moving saw blades. These guard members are often fixed in position, and to permit a work piece to meet the blade, can leave a substantial portion of the blade dangerously exposed. Others are expensive and complicated.
Taylor et al., U.S. Pat. No. 4,875,398, issued on Oct. 24, 1989, teaches a retractable dust control and safety hood for a rotary table saw. A hood is attached by counterbalanced linkages to a beam support structure so that the hood can be pivoted down against a work piece and then up and out of the way. A vacuum hose evacuates saw dust from within the hood and carries it out through the support structure. The hood has a window through which to view the saw operation. A problem with Taylor et al. is that the linkages, counterbalance mechanism, vacuum hose and assembly make the protective hood apparatus bulky and expensive. Another problem with Taylor et al. is that the moving saw blade remains dangerously exposed until the work piece advances under the hood and the hood is lowered against it.
Macksoud, U.S. Pat. No. 4,614,140, issued on Sep. 30, 1986, discloses a guard for a rocking arm saw having a circular disk blade which can be pivoted up through a slot in a saw table. The pivoting blade mounting structure has a handle extending over the back of the table, and the guard is pivotally mounted on an arm extending from the blade handle toward the blade. In this way, as the blade is rocked up through the slot, the guard rocks up with the blade. The guard is spaced above the table to clear a work piece being cut, and the forward end of the guard tilts down to cover the teeth of the blade as the guard and blade rock toward the operator. Macksoud has an alternative configuration for rip sawing wherein the blade continuously protrudes through the slot. The guard is pivotally attached to an end of a mounting arm, and the other end of the arm is pivotally attached to a vertical stand. The work piece is slid under an angled front edge of the guard and gradually tilts the guard upward as the work piece moves under it. A problem with Macksoud is that its structure limits its use to saws having the blade protruding up through a slot in a table. Another problem is that no provision is made for automating the guard, and manual operation can limit assembly line speed.
Kaiser et al., U.S. Pat. No. 4,581,966, issued on Apr. 15, 1986, reveals a chop saw linkage system with a swinging blade guard. The blade is a circular disk type and is rotatably mounted within a housing covering the upper half of the blade. The housing is itself pivotally mounted at an end so that the blade and housing can be lowered to make a saw cut and then tilted back up to a stable rest position. Kaiser et al. provides a guard member rotatably mounted on the blade axle and guard linkages contained within the housing. The linkages cause the guard member to swing over and cover the exposed part of the blade when the housing is raised, and to swing to expose the blade when the housing and blade are lowered to make a cut. A problem with Kaiser et al. is that the linkage structure limits the automatic guard to use on chop saws.
Elmaraghy et al., U.S. Pat. No. 4,549,456, issued on Oct. 29, 1985, teaches a noise damping guard for circular table saws. Elmaraghy et al. includes an upper guard mounted on a pivoting arm structure above the table and a lower guard secured around the blade slot under the table. The noise damping is effected by a sandwich material closely spaced to the saw blade side walls for destroying some of the blade vibratory energy. The sandwich material has high transmission loss and barrier characteristics and can withstand blade contact. A problem with Elmaraghy et al. is that the upper guard and lower guard must be separated to insert a work piece, thereby exposing a substantial segment of the blade cutting edge. Another problem is that the noise dampening layers of material and the support structure make Elmaraghy et al. costly.
Lavis, U.S. Pat. No. 4,163,404, issued on Aug. 7, 1979, discloses a circular power saw assembly which can be mounted to rotate horizontally on a table. Lavis is not directed to a saw guard, but includes a guard which is described as conventional. The guard rotates on the blade axle and is spring-loaded. A problem with Lavis is that the guard only covers a certain portion of the blade cutting edge, and rotating the guard leaves the same portion of the cutting edge dangerously exposed.
It is thus an object of the present invention to provide a saw guard which is adapted for use on a radial arm saw.
It is another object of the present invention to provide such a saw guard which can operate in conjunction with an existing, stationary guard to completely cover the blade cutting edge between saw cuts.
It is still another object of the present invention to provide such a saw guard which automatically opens to expose the blade for a saw cut and automatically closes upon completion of the cut.
It is finally an object of the present invention to provide such a saw guard which is simple, reliable, and inexpensive to manufacture.